Since my last post, I dropped by an Apple Store to take a look at the 2015 MacBook. It is difficult to overstate how startlingly small the new machine is in person. I may be biased by the internal specifications, but the impression is much more 'big tablet' than 'small laptop'. The other standout feature was the touchpad. It continues Apple's tradition of high-quality touchpad implementations, removes the mechanicical switch and hinge, and adds force sensititivy and haptic feedback. The mechanical simplifications alone are a worthwhile improvement.
I also spent some time typing on the keyboard. It's as shallow as you'd think, but the keys are very direct have a positive feel. There's none of the subtle rattling found on most small keyboards and it registered every keypress. I'm not completely convinced yet, but it at least seems possible that this type of keyboard could become the preferred keyboard for some typists.
The performance of the machine is also a point of interest. Even the lightly loaded demo machine on the showroom floor had a few hiccups paging the display around from one virtual desktop to the next. Maybe it's nothing, but it does make me wonder if the machine can keep up with daily use, particuarly after a few OSX updates have been released. (For me, I think it'd be fine, but I spend most my time in Terminal, Emacs, and Safari, none of which are exactly heavy-hitters.)